TN and STN liquid-crystal display

ABSTRACT

The invention relates to TN liquid-crystal displays and supertwist liquid-crystal displays (SLCDs) having very short response times and good steepnesses and angle dependences, and to the novel nematic liquid-crystal mixtures used therein, which are distinguished by the fact that they comprise at least one compound o the formula IA ##STR1## and at least one compound of the formula IB ##STR2## in which R a , R b , R c , Ring A*, L, l and r are as defined in claim 1.

The invention relates to TN liquid-crystal displays and supertwist liquid-crystal displays (SLCDs) having very short response times and good steepnesses and angle dependencies, and to the novel nematic liquid-crystal mixtures used therein.

SLCDs as define din the preamble are known, for example from EP 0 131 216 B1; De 34 23 993 A1; EP 0 098 070 A2; M. Schadt and F. Leenhouts, 17th Freiburg Congress on Liquid Crystals (8.-10.04.87); K. Kawasaki et al., SID 87 Digest 391 (20.6); M. Schadt and F. Leenhouts, SID 87 Digest 372 (20.1); K. Katch et al., Japanese journal of Applied Physics, Vol. 26, No. 11, L 1782-L 1786 (1987); F. Leenhouts et al., Appl. Phys. Lett. 50 (21), 1468 (1987); H. A. van sprang and H. G. Koopman, J. Appl. Phys. 62 (5), 1734 (1987); T. J. Scheffer and J. Nehring, Appl. Phys. Lett. 45 (10), 1021 (1984), M. Schadt and F. Leenhouts, Appl. Phys. Lett. 50 (5), 236 (1987) and E. P. Raynes, Mol. Cryst. Liq. Cryst. Letters Vol. 4 (1), pp. 1-8 (1986). The term SLCD here covers any more highly twisted display element with a value for the twist angle of between 160° and 360°, such as, for example, the display elements of Waters et al. (C. M. Waters et al., Proc. Soc. Inf. Disp. (New York) (1985) (3rd Intern. Display Conference, Kobe, Japan), STN-LCDs (DE-A-35 03 259), SBE-LCDs (T. J. Scheffer and J. Nehring, Appl. Phys. Lett. 45 (1984) 1021), OMI-LCDs (M. Schadt and F. Leenhouts, Appl. Phys. Lett. 50 (1987), 236, DST-LCDs (EP-A 0 246 842) or BW-STN-LCDs (K. Kawasaki et al., SID 87 Digest 391 (20.6)).

SLCDs of this type are distinguished, in comparison to standard TN displays, by significantly better steepnesses of the electrooptical characteristic line and consequently better contrast values, and by significantly less angle dependence of the contrast. Of particular interest are SLCDs having very short response times, in particular also at relatively low temperatures. In order to achieve short response times, the viscosities, in particular, of the liquid-crystal mixtures were hitherto optimized using usually monotropic additives having relatively high vapour pressure. However, the response times achieved were not adequate for all applications.

In order to achieve a steep electrooptical characteristic line, the liquid-crystal mixtures should have relatively large values for K₃ /K₁ and relatively small values for Δε/ε₁.

In addition to optimization of the contrast and the response times, further important requirements are made of mixtures of this type:

1. A broad d/p window

2. High long-term chemical stability

3. High electrical resistance

4. Low frequency dependence of the threshold voltage.

The parameter combinations achieved are still far from adequate, in particular for high-multiplex STNs (1/400). This is in some cases attributable to the fact that the various requirements are affected in opposite manners by material parameters.

There thus continues to be a great demand for TN and STN displays having very short response times and at the same time a large operating temperature range, high characteristic line steepness, good angle dependence of the contrast and low threshold voltage which meet the abovementioned requirements.

The invention has the object of providing liquid-crystal displays which do not have the abovementioned disadvantages, or only do so to a lesser extent, and at the same time have very good response times and very good steepnesses.

It has now been found that this object can be achieved if nematic liquid-crystal mixtures are used which comprise esters of the formula IA ##STR3## in which

R^(a) is an alkyl group having 1 to 12 carbon atoms, in which, in addition, one or two non-adjacent CH₂ groups may be replaced by --O--, --CH═CH--, --CO--, --OCO-- or --COO--,

L is H or F, and

r is 0 or 1,

in combination with alkenyl compounds of the formula IB ##STR4## in which

R^(b) is alkenyl having 2 to 12 carbons atoms,

R^(c) is F, an unsubstituted or at least monofluoro-substituted alkyl or alkoxy radical having 1-6 carbon atoms, ##STR5## are each, independently of one another, ##STR6##

l is 0 or 1, and

L¹ and L² are each, independently of one another, H or F.

The use of compounds of the formulae IA and IB in TN and STN mixtures produces

low viscosity and low temperature dependence of the viscosity at moderate μn,

long shelf lives in the display at low temperatures,

very fast S→N transitions,

low threshold voltages, and

very fast response times, in particular at low temperatures.

The compounds of the formulae IA and IB significantly shorten the response times of TN and STN mixtures without impairing the steepnesses.

The invention thus relates to a liquid-crystal display containing

two outer plates which, together with a frame, form a cell,

a nematic liquid-crystal mixture of positive dielectric anisotropy which is present in the cell,

electrode layers with alignment layers on the insides of the outer plates,

a pretilt angle between the longitudinal axis of the molecules at the surface of the outer plates and the outer plates of from about 0 degree to 30 degrees, and

a twist angle of the liquid-crystal mixture in the cell from alignment layer to alignment layer with a value of between 22.5° and 600°,

a nematic liquid-crystal mixture comprising

a) 20-90% by weight of a liquid-crystalline component A consisting of one or more compounds having a dielectric anisotropy of greater than +1.5;

b) 10-65% by weight of a liquid-crystalline component B consisting of one or more compounds having a dielectric anisotropy of between -1.5 and +1.5;

c) 0-20% by weight of a liquid-crystalline component D consisting of one or more compounds having a dielectric anisotropy of below -1.5, and

d) if desired, an optically active component C in such an amount that the ratio between the layer thickness (separation of the outer plates) and the natural pitch of the chiral nematic liquid-crystal mixture is from about 0.2 to 1.3,

characterized in that component A comprises at least one compound of the formula IA ##STR7## in which

R^(a) is an alkyl group having 1 to 12 carbon atoms, in which, in addition, one or two non-adjacent CH₂ groups may be replaced by --O--, --CH═CH--, --CO--, --OCO-- or --COO--,

L is H or F, and

r is 0 or 1,

and component B comprises at least one compound of the formula IB ##STR8## in which

R^(b) is an alkenyl radical having 2 to 12 carbon atoms,

R^(c) is F, or an unsubstituted or at least monofluoro-substituted alkyl or alkoxy radical having 1-6 carbon atoms, ##STR9## are each, independently of one another, ##STR10##

l is 0 or 1, and

L₁ and L₂ are each, independently of one another, H or F.

The invention also relates to corresponding liquid-crystal mixtures for use in STN and TN displays.

Preferred compounds of the formula IA are, in particular, compounds of the subformulae IA1 and IA2 (L=H or F): ##STR11##

Preferred compounds of the formula IB are, in particular, compounds of the subformulae IB1 to IB6: ##STR12## where

R^(c') is a straight-chain alkyl or alkoxy radical having 1-6 carbon atoms, and

R^(d) is H, CH₃, C₂ H₅ or n--C₃ H₇.

Component A preferably comprises, in addition to the compounds of the formula IA, compounds of the formulae II and/or III ##STR13## in which

R is an alkyl group having 1 to 12 carbon atoms, in which, in addition, one or two non-adjacent CH₂ groups may be replaced by --O--, --CH═CH--, --CO--, --OCO-- or --COO--, in particular a transalkenyl group having 2 to 7 carbon atoms, ##STR14## are each, independently of one another, ##STR15##

L¹⁻⁶ are each, independently of one another, H or F,

Z¹ is --COO--, --CH₂ CH₂ -- or a single bond,

Z² is --CH₂ CH₂ --, --COO--, --C═C-- or a single bond,

Q is --CF₂ --, --CHF--, --OCF₂ --, --OCHF-- or a single bond,

Y is F or Cl

a is 1 or 2, and

b is 0 or 1.

Preferred compounds of the formula II conform to the subformulae IIa to IId; ##STR16## in which R, L¹, L² and L⁵ are as defined above.

Preferred compounds of the formula III conform to the subformulae IIIa-IIIt (L³ and L⁴ =H or F): ##STR17##

In addition to one or more compounds of the formula IA and IB, preferred mixtures comprise one, two, three, or more compounds of the formulae IIa, IIb, IIc, IId, IIIb, IIId, IIIf, IIIh, IIIi, IIIm or IIIs, preferably one or more compounds of the formula IIIb, IIId or IIIh, and one to four compounds of the formulae IA and IB and one to three compounds of the formulae IIa and/or IIb.

The individual compounds, for example, of the formulae II and III or their subformulae or alternatively other compounds which can be used in the novel TN liquid-crystal displays and SLCDs are either known or can be prepared analogously to the known compounds.

In a particularly preferred embodiment, component A additionally comprises compounds of the formulae AI to AV: ##STR18## in which

R is an alkyl group having 1 to 12 carbon atoms, in which, in addition, one or two non-adjacent CH₂ groups may also be replaced by --O--, --CH═CH--, --CO--, --OCO-- or --COO--, in particular a trans-alkenyl group having 2 to 7 carbon atoms,

Q¹ ##STR19##

L⁵ and L⁶ are each, independently of one another, H or F,

Z³ is ##STR20## --CO--O--, --O--CO-- or a single bond, and ##STR21##

The mixture preferably comprise from 5 to 50% of compounds of the formula IA. Preference is given to compounds of the formula II in which Z¹ is --CH₂ CH₂ --, --COO-- or a single bond, in particular compounds of the formulae IIa1, IIb1, IId1, IIa2 and IIb2: ##STR22##

Component A preferably comprises one or more compounds of the formulae IIb1.

The novel mixtures preferably comprise one or more polar compounds having a high clearing point selected from the group consisting of the compounds IIe to IIi: ##STR23##

In the compounds IIe to IIi, the 1,4-phenylene rings can also be laterally substituted by one or two fluorine atoms. Preferred compounds of this type are the compounds of the formulae IIe1, IIe2, IIe3 and IIi1: ##STR24##

In the novel mixtures, the proportion of compounds IIe to IIi is preferably from about 2 to 25%.

Preferred liquid-crystal mixtures comprise one or more compounds from Group B, preferably 10 to 40%. The compounds from Group B are distinguished both by their low rotational viscosity (γ₁) values of <150 mPa·s and by their high clearing point (>120° C.).

Component B preferably, in addition to one or more compounds of the formula IB, comprises one or more compounds selected from the group consisting of the compounds of the formulae IV1 to IV9: ##STR25## in which R¹ and R² are as defined for R.

In a particularly preferred embodiment, the novel mixture comprises at least one compound of the formula IV1 and/or IV1.

Component B additionally comprises one or more compounds selected from the group consisting of the compounds of the formulae IV10 to IV14: ##STR26## in which R¹ and R² are as defined for R, and the 1,4-phenylene groups in IV10 to IV19, IV12 and IV23 may each, independently of one another, also be monosubstituted or polysubstituted by fluorine.

In a particularly preferred embodiment, the novel media comprise at least one compound of the formulae IA and IB and at least one compound of the formulae IV12 and/or IV16, in which R¹ is trans-alkenyl having 2 to 10 carbon atoms, in particular 1E-alkenyl or 3E-alkenyl.

Component B additionally, in addition to component IB, comprises one or more compounds selected from the group consisting of the compounds of the formulae IV25 to IV30: ##STR27## in which R¹ and R² are as defined for R, and the 1,4-phenylene groups in IV25 to IV30 may also each, independently of one another, be monosubstituted or polysubstituted by fluorine.

Component B optionally comprises one or more compounds selected from the group consisting of the compounds of the formula IV31 and IV32: ##STR28## in which C_(r) H_(2r+1) is a straight-chain alkyl group having up to 9 carbon atoms.

The novel liquid-crystal mixture may furthermore comprise one or more compounds selected from the group ##STR29## in which R¹ and R² are as defined for R.

Preferred liquid-crystal mixtures comprise at least one component selected from the group consisting of the following compounds: ##STR30## in which Hal is F or Cl, L is H or F, and R and R¹ are as defined above.

The liquid-crystal mixtures optionally comprise an optically active component C in such an amount that the ratio between the layer thickness (separation of the outer plates) and the natural pitch of the chiral nematic liquid-crystal mixture is greater than 0.2. For the component, a multiplicity of chiral dopes, some commercially available, is available to the person skilled in the art, for example such as cholesteryl nonanoate, S-811 form Merck KGaA, Darmstadt, FRG, and CB 15 (BDH, Poole, UK), as well as C 15, exemplified in Table B. The choice of dopes is not crucial per se.

Component D comprises compounds with a dielectric anisotropy below -1.5 such as, e.g., those disclosed in WO 89/08633, U.S. Pat. No. 5,204,019 and U.S. Pat. No. 5,248,447.

The novel liquid-crystal mixture preferably comprises one or more compounds selected from Group B1 consisting of compounds of the formulae B1I to B1IV: ##STR31## in which

R¹ and R² are each, independently of one another, as defined for R,

Z is --CH₂ CH₂ --, --CO--O--, --O--CO-- or a single bond, and, ##STR32## and/or at least one compound selected from Group B2 consisting of compounds of the formulae B1V to B1VII: ##STR33## in which

R is as defined above,

Z⁰ is --COO--, --CH₂ CH₂ -- or a single bond,

Q⁰ is ##STR34## where r is 1-9,

X is CN or F,

L¹ is H or F,

and/or at least one compound selected from Group B3 consisting of compounds of the formulae B1VIII, B1IX and B1X: ##STR35## in which

R¹ and R², independently of one another, are as defined for R,

Y is F or Cl, and ##STR36##

In a particularly preferred embodiment, the novel mixtures comprise from about 5 to 35%, in particular from 10 to 20%, of liquid-crystalline tolan compounds. This enables smaller layer thicknesses (about 5-6 μm) to be used, significantly shortening the response times. Particular preference is given to mixtures comprising one or more compounds selected from Group T consisting of the compounds of the formulae T1 to T3: ##STR37## in which

Q² is ##STR38## preferably ##STR39##

L¹, L², L⁵ and L⁶ are each, independently of one another, H or F

Q is --CF₂ --, --CHF--, --OCF₂ --, --OCHF-- or a single bond,

Y is F or Cl,

Z⁰ is --CO--O--, --CH₂ CH₂ -- or single bond, and

R¹ and R² are each, independently of one another, as defined for R,

R⁷ is --C_(x) H_(2x-1), --OC_(x) H_(2x+1), ##STR40##

x is an integer from 1 to 15, and

X' is F, Cl or OCF₃.

The proportion of compounds from the group T is preferably from 5 to 30%, in particular from 5 to 20%.

Component B preferably comprises one or more compounds of the formulae X to XIII: ##STR41## in which

R¹ and R² are each, independently of one another, as defined for R.

Preferred tolans of component B are compounds selected from the group consisting of Xa to XIIIa ##STR42## in which Alkyl and Alkoxy are a straight-chain alkyl or alkoxy radical having 1 to 7 carbon atoms.

The proportion of compounds from group B1 is preferably from 10 to 50%, in particular from 15 to 40%. Compounds of the formula B1III and B1IV are preferred.

Particularly preferred compounds of the formula B1III are those of the following subformulae B1IIIa and B1IIIb ##STR43## in which

R^(3') is CH₃ --(CH₂)_(o) --, CH₃ --(CH₂)_(o) --O--, CH₃ --(CH₂)_(P) --, trans-H-(CH₂)_(q) --CH═CH--(CH₂ CH₂)_(b) --CH₂ O-- or trans-H-(CH₂)_(q) --CH═CH--(CH₂ CH₂)_(b) --, CH₃ --(CH₂)₀ --O--CH₂ --,

R^(4') is CH₃ --(CH₂)_(p) --,

o is 1, 2, 3 or 4,

q is 0, 1, 2 or 3,

b is 0 or 1, and

p is 1, 2, 3 or 4.

Particular preference is given to compounds of the formula B1IIIa in which R3' is trans-H-(CH₂)_(q) --CH═CH-- and the formula B1III in which one of the radicals R^(3') or R^(4') is O--(CH₂)_(o) --CH₃ or CH₂ --O--(CH₂)_(o) --CH₂ --.

Preference is furthermore given to the compounds of the subformula ##STR44## in which R^(3') and R^(4') are each, independently of one another, as defined above.

The proportion of compounds of the formula B1III of the abovementioned subformulae is preferably from about 5 to 45%, particularly preferably from about 10% to 35%. Particularly preferred compounds of the formula B1IV are those of the following subformula ##STR45## in which

R* is CH₃ --(CH₂ _(o) --O-- or trans -H-(CH₂)_(q) --CH═CH--(CH₂ CH₂)_(b) --CH₂ O--, and

R^(2') is CH₃ --(CH₂)_(p) --, where

o is 0, 1, 2, 3 or 4,

q is 0, 1, 2 or 3,

b is 0 or 1, and

p is 1, 2, 3 or 4.

The proportion of these compounds or of compounds of the formula BIV is preferably from about 5 to 40%, particularly preferably from about 10 to 35%.

In a particularly preferred embodiment, the mixtures simultaneously comprise compounds of the formulae B1III and B1IV, where the total proportion of components from group B1 remains observed.

If compounds of the formulae B1I and B1III are present, R¹ and R² are preferably each, independently of one another, n-alkyl having 1 to 7 carbon atoms or (trans)-n-alkenyl having 3 to 7 carbon atoms. Z is preferably a single bond.

Preference is furthermore given to novel mixtures which comprise one or more compounds of the formula B1IV in which ##STR46## and R¹ and R² have one of the preferred meanings given above, particularly preferably n-alkyl having 1 to 7 carbon atoms.

In all cases, the total proportion of components from group B1 remains observed.

The proportion of compounds from group B2 is preferably from about 5 to 45%, in particular from 5 to 20%. The proportion (preferred ranges) for B1V to B1VII is as follows:

B1V: from about 5 to 30%,preferably from about 5 to 15% Sum of B1VI

and B1VII: from about 5 to 25%, preferably from about 10 to 20%.

Preferred compounds from group B2 are shown below: ##STR47##

R¹ is preferably n-alkyl having 1 to 7 carbon atoms or (trans)-n-alkenyl having 2 to 7 carbon atoms. Z⁰ is preferably a single bond. R¹ preferably has the preferred meaning given above for R or is fluorine. L¹ is preferably fluorine, x is 1-15.

The novel mixtures preferably comprise one or more compounds selected from the group consisting of B1V3, B1VI1 and B1VII1 in a total proportion of from about 5 to 35%.

In a particularly preferred embodiment, the novel mixtures, in addition to B1V3, B1VI1 and B1VII1 (L¹ =F), comprise further terminally fluorinated compounds selected, for example, from the group consisting of ##STR48## and/or polar heterocyclic compounds selected from the group consisting of ##STR49## in which R¹ is preferably n-alkyl having 1 to 7 carbon atoms or (trans)-n-alkenyl having 2 to 7 carbon atoms, a is 1 or 2, b is 0 or 1, X^(o) is F, Cl, CF₃, --OCF₃ or --OCHF₂, and L is H or F.

The total proportion of all terminally fluorinated compounds is preferably from about 5 to 65%, in particular from about 15 to 40%.

The proportion of compounds from group B3 is preferably from about 5 to 30%, particularly preferably from about 10 to 20%. R¹ is preferably n-alkyl or n-alkoxy, in each case having 1 to 9 carbon atoms.

However, it is also possible to use analogous compounds containing alkenyl or alkenyloxy groups. Compounds of the formula B1VIII are preferred.

The novel mixtures comprise compounds of the formulae IA and IB and preferably compounds from at least one of groups B1, B2 and B3. They preferably comprise one or more compounds from group B1 and one or more compounds from group B2 and/or B3.

The proportion of compounds of component C i s preferably from 0 to 20%, in particular from 0 to 10%.

Further particularly preferred embodiments are given below:

Component C comprises, e.g., one or more compounds containing a 1-cyano-trans-1,4-cyclohexyl group or a 2,3-difluoro-1,4-phenylene group

at least two compounds of the formulae AIII or AV

compounds of the formulae AIII and AV

at least one compound from the group consisting of: ##STR50## in which Alkyl is a straight-chain alkyl or alkoxy radical having 2 to 7 carbon atoms, and L is H or F;

one or more compounds in which R is a trans-alkenyl group or a trans-alkenyloxy group;

one or more compounds selected from the following group: ##STR51## in which R¹ and R² have the preferred meanings given under compounds of component B. The 1,4-phenylene groups in the abovementioned compounds can also be substituted by fluorine. The proportion of these compounds in the liquid-crystal mixtures is from 0 to 25%, preferably from 5 to 15%.

In a further preferred embodiment, the mixtures comprise

one or more, in particular 1, 2, 3 or 4, compounds selected from the compounds of the formulae IIb, IIId, IIIf, IIIh and IIIi;

at least two compounds selected from the compounds of the formulae IIa1, IIb1 and IIb2;

one or more compounds of the formula B1IV;

one or more compounds of the formula T1 to T2;

one or more compounds of the formulae ##STR52## in which R is as defined under the formula III.

In a preferred embodiment, the novel liquid-crystalline media comprise 3, 4, 5 or 6 compounds of the formula IA and/or IB; the content of these compounds is generally from 10 to 60% by weight, preferably from 15 to 50% by weight, based on the overall mixture.

Media comprising compounds of the formula IB in which R^(b) is 1E-alkenyl or 3E-alkenyl are particularly preferred. R^(b) is in particular CH₂ ═CH-- or CH₃ --CH═CH--.

In particular when use din SLCDs and TN displays having high layer thicknesses, the novel mixtures are distinguished by very low overall response times (=t_(on) +t_(off)).

Low overall response times are an important criterion, in particular, in SLCDs for use as displays in laptops in order to be able to display cursor movements without interference.

The liquid-crystal mixtures used in the STN and TN cells according to the invention are dielectrically positive with Δε≧1. Particular preference is given to liquid-crystal mixtures where Δε≧3 and very particularly to those where Δε≧5.

The liquid-crystal mixtures according to the invention have favourable values for the threshold voltage V_(10/0/20) and for the flow viscosity ν. If the value for the optical path difference d.Δn is specified, the value for the layer thickness d is determined by the optical anisotropy Δn. In particular at relatively high values for d.Δn, the use of liquid-crystal mixtures according to the invention having a relatively high value for the optical anisotropy is generally preferred since the value for d can then be chosen to be relatively small, which results in more favourable values for the response times. However, liquid-crystal displays according to the invention which contain liquid-crystal mixtures according to the invention having relatively small values for Δn are also characterized by advantageous values for the response times. The liquid-crystal mixtures according to the invention are furthermore characterized by advantageous values for the steepness of the electrooptical characteristic line and can be operated at high multiplex rates. In addition, the liquid-crystal mixtures according to the invention have high stability and favourable values for the electrical resistance and the frequency dependence of the threshold voltage. The liquid-crystal displays according to the invention have a broad operating temperature range and good angle dependence of the contrast.

The construction of the liquid-crystal display elements according to the invention from polarizers, electrode baseplates and electrodes with a surface treatment such that the preferential alignment (director) of the liquid-crystal molecules in each case adjacent thereto is usually twisted by a value of from 160° to 720° from one electrode to the next, corresponds to the structure which is conventional for display elements of this type. The term conventional structure here is broadly drawn and also includes all derivatives and modifications of the TN and STN cell, in particular also matrix display elements, and display elements which contain additional magnets. The surface tilt angle at the two outer plates may be identical or different. Identical tilt angles are preferred. Preferred TN displays have pretilt angles between the longitudinal axis of the molecules at the surface of the outer plates and the outer plates of from 0° to 7°, preferably from 0.01° to 5°, in particular from 0.1 to 2°. In STN displays, the pretilt angle is from 1° to 30°, preferably from 1° to 12°, in particular from 3° to 8°.

The twist angle of the TN mixture in the cell has a value of between 22.5° and 170°, preferably between 45° and 130°, in particular between 80° and 115°. The twist angle of the STN mixture in the display from alignment layer to alignment layer has a value of between 100° and 600°, preferably between 170° and 270°, in particular between 180° and 250°.

The liquid-crystal mixtures which can be used according to the invention are prepared in a manner which is known per se. In general, the desired amount of the components used in a lesser amount is dissolved in the components making up the principal constituent, expediently at elevated temperature. It is also possible to mix solutions of the components in an organic solvent, for example in acetone, chloroform or methanol, and, after mixing, to remove the solvent again, for example by distillation.

The dielectrics may also contain further additives which are known to a person skilled in the art and are described in the literature. For example, 0-15% of pleochroic dyes may be added.

The examples below are intended to illustrate the invention without representing a limitation.

The following abbreviations are used:

S-N smectic-nematic phase transition temperature,

N-I nematic-isotropic phase transition temperature,

c.p. clearing point,

t_(on) time from switching on until 90% of the maximum contrast is achieved,

t_(off) time from switching off until 10% of the maximum contrast is achieved,

V₉₀ /V₁₀ steepness,

t_(ave) ##EQU1## (average response time).

The SLCD is operated in multiplex mode (multiplex ratio 1:240, bias 1:16, operating voltage 10 volts, so that t_(on) =t_(off)).

Above and below, all temperatures are indicated in ° C. The percentages are percent by weight. The values for the response times and viscosities relate to 20° C.

In the present application and in the examples below, the structures of the liquid-crystal compounds are indicated by acronyms, the transformation into chemical formulae taking place in accordance with tables A and B below. All radicals C_(n) H_(2n+1) and C_(m) H_(2m+1) are straight-chain alkyl radicals having n and m carbon atoms respectively. The alkenyl radicals have the trans configuration. The coding in Table B is self-evident. In Table A, only the acronym for the parent structure is given. In individual cases, the acronym for the parent structure is followed, separated by a dash, by a code for the substituents R¹, R², L¹, L² and L³ :

    __________________________________________________________________________     Code for                                                                       R.sup.1, R.sup.2,                                                              L.sup.1, L.sup.2, L.sup.3                                                           R.sup.1      R.sup.2        L.sup.4                                                                          L.sup.2                                                                          L.sup.5                                   __________________________________________________________________________     nm   C.sub.n H.sub.2n+1                                                                          C.sub.m H.sub.2m+1                                                                            H H H                                         nOm  C.sub.n H.sub.2n+1                                                                          OC.sub.m H.sub.2m+1                                                                           H H H                                         nO.m OC.sub.n H.sub.2n+1                                                                         C.sub.m H.sub.2m+1                                                                            H H H                                         n    C.sub.n H.sub.2n+1                                                                          CN             H H H                                         nN.F C.sub.n H.sub.2n+1                                                                          CN             H H F                                         nF   C.sub.n H.sub.2n+1                                                                          F              H H H                                         nOF  OC.sub.n H.sub.2n+1                                                                         F              H H H                                         nCl  C.sub.n H.sub.2n+1                                                                          Cl             H H H                                         nF.F C.sub.n H.sub.2n+1                                                                          F              H H F                                         nmF  C.sub.n H.sub.2n+1                                                                          C.sub.m H.sub.2m+1                                                                            F H H                                         nCF.sub.3                                                                           C.sub.n H.sub.2n+1                                                                          CF.sub.3       H H H                                         nOCF.sub.3                                                                          C.sub.n H.sub.2n+1                                                                          OCF.sub.3      H H H                                         nOCF.sub.2                                                                          C.sub.n H.sub.2n+1                                                                          OCHF.sub.2     H H H                                         nS   C.sub.n H.sub.2n+1                                                                          NCS            H H H                                         rVsN C.sub.r H.sub.2r+1 --CH═CH--C.sub.g H.sub.2g --                                         CN             H H H                                         rEsN C.sub.r H.sub.2r+1 --O--C.sub.2 H.sub.2g --                                                 CN             H H H                                         nNF  C.sub.n H.sub.2n+1                                                                          CN             H F H                                         nAm  C.sub.n H.sub.2n+1                                                                          COOC.sub.m H.sub.2m+1                                                                         H H H                                         nF.Cl                                                                               C.sub.n H.sub.2n+1                                                                          Cl             H H F                                         n-Vm C.sub.n H.sub.2n+1                                                                          --CH═CH--C.sub.m H.sub.2m+1                                                               H H H                                         nV-Vm                                                                               C.sub.n H.sub.2n+1 --CH═CH--                                                            --CH═CH--C.sub.m H.sub.2m+1                                                               H H H                                         nV-m C.sub.n H.sub.2n+1 --CH═CH--                                                            --C.sub.m H.sub.2m+1                                                                          H H H                                         nV-N C.sub.n H.sub.2n+1 --CH═CH--                                                            --CN           H H H                                         nV-F C.sub.n H.sub.2n+1 --CH═CH--                                                            F              H H H                                         nV-F.F                                                                              C.sub.n H.sub.2n+1 --CH═CH--                                                            F              H H F                                         n-2Vm                                                                               C.sub.n H.sub.2n+1                                                                          C.sub.m H.sub.2m+1 --CH═CH--CH.sub.2 CH.sub.2                                             H-                                                                               H H                                         __________________________________________________________________________

The TN and STN displays preferably contain liquid-crystalline mixtures composed of one or more compounds from Tables A and B.

                                      TABLE A                                      __________________________________________________________________________     (L.sup.1, L.sup.2, L.sup.3 = H or F)                                           __________________________________________________________________________      ##STR53##                                                                                                      ##STR54##                                      ##STR55##                                                                                                      ##STR56##                                      ##STR57##                                                                                                      ##STR58##                                      ##STR59##                                                                                                      ##STR60##                                      ##STR61##                                                                                                      ##STR62##                                      ##STR63##                                                                      ##STR64##                                                                      ##STR65##                                                                      ##STR66##                                                                                                      ##STR67##                                     __________________________________________________________________________

                                      TABLE B                                      __________________________________________________________________________      ##STR68##                                                                                                 ##STR69##                                           ##STR70##                                                                                                 ##STR71##                                           ##STR72##                                                                      ##STR73##                                                                                                 ##STR74##                                           ##STR75##                                                                      ##STR76##                                                                      ##STR77##                                                                                                 ##STR78##                                           ##STR79##                                                                      ##STR80##                                                                                                 ##STR81##                                          __________________________________________________________________________

The examples below are intended to illustrate the invention without representing a limitation. Above and below, percentages are percent by weight. All temperatures are given in degrees celcius. m.p. denotes melting point, c.p.=clearing point. Furthermore, C=crystalline state, N=nematic phase, S=smectic phase and I=isotropic phase. The numbers between these symbols are the transition temperatures. Δn denotes optical anisotropy (589 nm, 20° C.), and the viscosity (mm² /sec) was determined at 20° C.

The entire disclosure of all applications, patents and publications, cited above and below, and of corresponding German application No. 196 44 042.4, filed Oct. 31, 1996 is hereby incorporated by reference.

EXAMPLE 1

An STN mixture comprising

    ______________________________________                                         PCH-3    20.0%     S→N:    <-40° C.                              ME2N.F   3.0%      Clearing point:                                                                               +114.0° C.                            PCH-301  10.0%     Δn [589 nm; 20° C.]:                                                             +0.1691                                      PTP-102  5.0%      HTP (S-811):   -9.9                                         PTP-201  5.0%      Twist:         180°                                  CPTP-301 6.0%      V.sub.(10,0,20) :                                                                             2.30 V                                       CPTP-302 6.0%      d/p:           0.45                                         CPTP-303 6.0%      d · Δn:                                                                        0.95                                         CPTP-30CF.sub.3                                                                         4.0%                                                                  CPTP-50CF.sub.3                                                                         4.0%                                                                  CCP-20CF.sub.3                                                                          4.0%                                                                  CCP-30CF.sub.3                                                                          4.0%                                                                  CP-33F   4.0%                                                                  CBC-33F  4.0%                                                                  CBC-53F  4.0%                                                                  CC-5-V   11.0%                                                                 ______________________________________                                    

EXAMPLE 2

A TN mixture comprising

    ______________________________________                                         ME2N.F   2.0%      S→N:    <-40° C.                              ME3N.F   2.0%      Clearing point:                                                                               +115.0° C.                            ME4N.F   2.0%      Δn [569 nm; 20° C.]:                                                             +0.0891                                      ME5N.F   2.0%      Twist:         90°                                   PYP-SF   8.0%      V.sub.(10,0,20) :                                                                             2.29 V                                       CCH-301  16.0%     d · Δn:                                                                        0.5                                          CC-5-V   13.0%                                                                 BCH-3F.F 8.0%                                                                  CH-33    4.0%                                                                  CC-35    4.0%                                                                  CH-43    4.0%                                                                  CH-45    4.0%                                                                  CP-33F   6.0%                                                                  CP-35F   6.0%                                                                  CP-55F   6.0%                                                                  CCPC-33  5.0%                                                                  CCPC-34  4.0%                                                                  CCPC-35  4.0%                                                                  ______________________________________                                    

EXAMPLE 3

A TN mixture comprising

    ______________________________________                                         ME2N.F   2.2%      S→N:    <-40° C.                              ME3N.F   1.7%      Clearing point:                                                                               +109.0° C.                            ME4N.F   3.1%      Δn [589 nm; 20° C.]:                                                             +0.0992                                      PYP-5F   8.0%      Twist:         90°                                   CCH-301  10.0%     V.sub.(10,0,20) :                                                                             2.29 V                                       CCH-303  6.0%                                                                  CCH-501  4.0%                                                                  PCH-301  3.9%                                                                  BCH-3F.F 9.0%                                                                  CC-5-V   13.0%                                                                 CP-33F   5.0%                                                                  CP-3SF   5.0%                                                                  CP-SSF   5.0%                                                                  CH-33    4.0%                                                                  CBC-33   4.0%                                                                  CBC-53   2.0%                                                                  CBC-55   3.0%                                                                  CBC-33P  3.0%                                                                  CCPC-33  2.0%                                                                  CCPC-34  4.0%                                                                  CCPC-35  2.0%                                                                  ______________________________________                                    

EXAMPLE 4

An STN mixture comprising

    ______________________________________                                         PCH-3    27.0%     S→N:    <-20° C.                              CC-5-V   8.0%      Clearing point:                                                                               +83.0° C.                             ME2N.F   4.0%      Δn [589 nm; 20° C.]:                                                             +0.1529                                      ME3N.F   3.0%      HTP (S-811):   -11.5                                        ME4N.F   10.0%     Twist:         220°                                  ME5N.F   9.0%      V.sub.(10,0,20) :                                                                             1.35 V                                       CPTP-30CF.sub.3                                                                         6.0%      d/p:           0.5                                          CPTP-50CF.sub.3                                                                         7.0%      d · Δn:                                                                        0.9                                          CCP-20CF.sub.3                                                                          3.0%                                                                  CP-33F   5.0%                                                                  CP-35F   5.0%                                                                  PTP-102  2.0%                                                                  PTP-201  3.0%                                                                  CPTP-302 2.0%                                                                  CBC-33   3.0%                                                                  CBC-53   3.0%                                                                  ______________________________________                                    

EXAMPLE 5

    ______________________________________                                         PCH-3    20.0%     S→N:    <-40° C.                              ME2N.F   3.0%      Clearing point:                                                                               +114.0° C.                            PCH-301  10.0%     Δn [589 nm; 20° C.]:                                                             +0.1691                                      PTP-102  5.0%      HTP (S-811):   -9.9                                         PTP-201  5.0%      Twist:         180°                                  CPTP-301 6.0%      V.sub.(10,0,20) :                                                                             2.30 V                                       CPTP-302 6.0%      d/p:           0.45                                         CPTP-303 6.0%      d · Δn:                                                                        0.95                                         CPTP-30CF.sub.3                                                                         6.0%                                                                  CPTP-50CF.sub.3                                                                         4.0%                                                                  CCP-20CF.sub.3                                                                          4.0%                                                                  CCP-30CF.sub.3                                                                          4.0%                                                                  CP-33F   4.0%                                                                  CBC-33F  4.0%                                                                  CBC-53F  4.0%                                                                  CC-5V    11.0%                                                                 ______________________________________                                    

EXAMPLE 6

A TN mixture comprising

    ______________________________________                                         ME2N.F   2.0%      S→N:    <-40° C.                              ME3N.F   2.0%      Clearing point:                                                                               +107.5° C.                            ME4N.F   3.0%      Δn [589 nm; 20° C.):                                                             +0.0995                                      PYP-5F   7.0%      Twist:         90°                                   CCC-301  10.0%     V.sub.(10,0,20) :                                                                             2.37 V                                       CCH-303  6.0%      d · Δn:                                                                        0.5                                          CCH-501  6.0%                                                                  PCH-301  5.0%                                                                  BCH-3F.F 9.0%                                                                  CC-5-V   12.0%                                                                 CP-33F   5.0%                                                                  CP-35F   5.0%                                                                  CP-55F   5.0%                                                                  CH-33    3.0%                                                                  CBC-33   4.0%                                                                  CBC-53   4.0%                                                                  CBC-55   3.0%                                                                  CBC-33F  3.0%                                                                  CCPC-33  2.0%                                                                  CCPC-34  2.0%                                                                  CCPC-35  2.0%                                                                  ______________________________________                                    

EXAMPLE 7

An STN mixture comprising

    ______________________________________                                         ME2N.F   5.0%      S→N:    <-30° C.                              ME3N.F   5.0%      Clearing point:                                                                               +90.0° C.                             ME4N,F   9.0%      Δn [569 nm; 20° C.]:                                                             +0.1209                                      ME5N.F   10.0%     Twist:         220°                                  ME7N.F   10.0%     V.sub.(10,0,20) :                                                                             1.09 V                                       HP-3N.F  5.0%                                                                  HP-4N.F  5.0%                                                                  HP-5N.F  5.0%                                                                  CCH-301  13.0%                                                                 CC-5-V   18.0%                                                                 CCPC-33  5.0%                                                                  CCPC-34  5.0%                                                                  CCPC-35  5.0%                                                                  ______________________________________                                    

EXAMPLE 8

A TN mixture comprising

    ______________________________________                                         ME2N.F   2.0%      S→N:    <-40° C.                              ME3N.F   2.0%      Clearing point:                                                                               +109.5° C.                            ME4N.F   3.5%      Δn [589 nm; 20° C.]:                                                             +0.0996                                      PYP-5F   8.0%      Twist:         90°                                   CCH-301  10.0%     V.sub.(10,0,20) :                                                                             2.31 V                                       CCH-303  6.0%                                                                  CCH-501  4.0%                                                                  PCH-301  3.5%                                                                  BCH-3F.F 9.0%                                                                  CC-5-V   13.0%                                                                 CP-33F   5.0%                                                                  CP-35F   5.0%                                                                  CP-55F   5.0%                                                                  CH-33    4.0%                                                                  CBC-33   4.0%                                                                  CBC-53   2.0%                                                                  CBC-55   3.0%                                                                  CBC-33F  3.0%                                                                  CCPC-33  2.0%                                                                  CCPC-34  4.0%                                                                  CCPC-35  2.0%                                                                  ______________________________________                                    

EXAMPLE 9

A TN mixture comprising

    ______________________________________                                         ME2N.F   2.0%      S→N:    <-40° C.                              ME3N.F   2.0%      Clearing point:                                                                               +15.0° C.                             ME4N.F   2.0%      Δn [599 nm; 20° C.]:                                                             +0.0891                                      ME5N.F   2.0%      Twist:         90°                                   PYP-5F   8.0%      V.sub.(10,0,20) :                                                                             2.29 V                                       CCH-301  16.0%                                                                 CC-5-V   13.0%                                                                 BCH-3F.F 8.0%                                                                  CH-33    4.0%                                                                  CH-35    4.0%                                                                  CH-43    4.0%                                                                  CH-45    4.0%                                                                  CP-33F   6.0%                                                                  CP-35F   6.0%                                                                  CP-55F   6.0%                                                                  CCPC-33  5.0%                                                                  CCPC-34  4.0%                                                                  CCPC-35  4.0%                                                                  ______________________________________                                    

EXAMPLE 10

An STN mixture comprising

    ______________________________________                                         ME2N.F   3.0%      S→N:    <-40° C.                              ME3N.F   3.0%      Clearing point:                                                                               +82.5° C.                             ME4N.F   5.0%      Δn [589 nm; 20° C.]:                                                             +0.1183                                      ME5N.F   5.0%      HTP (S-811):   -10.7                                        PCH-301  11.0%     Twist:         220°                                  CC-5-V   18.0%     V.sub.(10,0,20) :                                                                             1.94 V                                       PTP-102  4.0%                                                                  PTP-201  4.0%                                                                  CCP-20CF.sub.3                                                                          5.0%                                                                  CCP-30CF.sub.3                                                                          6.0%                                                                  ECCP-3F.F                                                                               5.0%                                                                  ECCP-5F.F                                                                               5.0%                                                                  BCH-3F.F 9.0%                                                                  CP-33F   5.0%                                                                  CP-35F   5.0%                                                                  CP-55F   5.0%                                                                  CPTP-302 2.0%                                                                  ______________________________________                                    

EXAMPLE 11

An STN mixture comprising

    ______________________________________                                         PCH-3    8.0%      S→N:    <-40° C.                              ME2N.F   3.0%      Clearing point:                                                                               +85.5° C.                             ME3N.F   3.0%      Δn [589 nm; 20° C.]:                                                             +0.1598                                      ME4N.F   6.0%      HTP (S-811):   -10.8                                        PCH-301  18.0%     Twist:         220°                                  CC-5-V   14.0%     V.sub.(10,0,20) :                                                                             1.99 V                                       PTP-102  5.0%                                                                  PTP-201  5.0%                                                                  BCH-3F.F 9.0%                                                                  CP-33F   6.0%                                                                  CPTP-301 6.0%                                                                  CPTP-302 5.0%                                                                  CPTP-303 3.0%                                                                  CPTP-30CF.sub.3                                                                         5.0%                                                                  CPTP-50CF.sub.3                                                                         4.0%                                                                  ______________________________________                                    

EXAMPLE 12

A TN mixture comprising

    ______________________________________                                         ME2N.F   2.2%      S→N:    <-40° C.                              ME3N.F   1.7%      Clearing point:                                                                               +109.0° C.                            ME4N.F   3.1%      Δn [599 nm; 20° C.]:                                                             +0.0992                                      PYP-5F   8.0%      Twist:         90°                                   CCH-301  10.0%     V.sub.(10,0,20) :                                                                             2.29 V                                       CCH-303  6.0%                                                                  CCH-501  4.0%                                                                  PCH-301  3.9%                                                                  BCH-3F.F 9.0%                                                                  CC-5-V   13.0%                                                                 CP-33F   5.0%                                                                  CP-35F   5.0%                                                                  CP-SSF   5.0%                                                                  CH-33    4.0%                                                                  CBC-33   4.0%                                                                  CBC-53   2.0%                                                                  CBC-55   3.0%                                                                  CBC-33F  3.0%                                                                  CCPC-33  2.0%                                                                  CCPC-34  4.0%                                                                  CCPC-35  2.0%                                                                  ______________________________________                                    

EXAMPLE 13

An STN mixture comprising

    ______________________________________                                         K6       5.0%      S→N:    <-40° C.                              ME2N.F   3.0%      Clearing point:                                                                               +86.0° C.                             ME3N.F   3.0%      Δn [589 nm; 20° C.]:                                                             +0.1599                                      ME4N.F   7.0%      HTP (S-811):   -10.6                                        PCH-301  17.0%     Twist:         220°                                  CC-5-V   16.0%     V.sub.(10,0,20) :                                                                             1.99 V                                       PTP-102  5.0%                                                                  PTP-201  5.0%                                                                  BCH-3F.F 8.0%                                                                  CP-33F   5.0%                                                                  CP-35F   5.0%                                                                  CPTP-301 4.0%                                                                  CPTP-302 5.0%                                                                  CPTP-303 4.0%                                                                  CPTP-30CF.sub.3                                                                         4.0%                                                                  CPTP-50CF.sub.3                                                                         4.0%                                                                  ______________________________________                                    

EXAMPLE 14

An STN mixture comprising

    ______________________________________                                         ME2N.F   4.0%      S→N:    <-40° C.                              ME3N.F   4.0%      Clearing point:                                                                               +95.5° C.                             ME4N.F   6.0%      Δn [589 nm; 20° C.]:                                                             +0.1073                                      ME5N.F   6.0%      HTP (CB-15):   -10.4                                        PCH-301  9.0%                                                                  CC-5-V   20.0%                                                                 CCP-20CF.sub.3                                                                          7.0%                                                                  CCP-30CF.sub.3                                                                          7.0%                                                                  ECCP-3F.F                                                                               3.0%                                                                  ECCP-5F.F                                                                               4.0%                                                                  BCH-3F.F 4.0%                                                                  BCH-5F.F 4.0%                                                                  CP-33F   4.0%                                                                  CP-35F   4.0%                                                                  CP-55F   4.0%                                                                  CBC-33F  4.0%                                                                  CBC-53F  4.0%                                                                  CBC-55F  2.0%                                                                  ______________________________________                                    

EXAMPLE 15

An STN mixture comprising

    ______________________________________                                         ME2N.F   3.0%      S→N:    <-40° C.                              ME3N.F   3.0%      Clearing point:                                                                               +87.5° C.                             ME4N.F   5.0%      Δn [589 nm; 20° C.]:                                                             +0.1215                                      ME5N.F   4.0%      HTP (S-811):   -10.6                                        PCH-3    5.0%      Twist:         220°                                  PCH-301  15.0%     V.sub.(10,0,20) :                                                                             2.06 V                                       CC-5-V   18.0%                                                                 PTP-102  4.0%                                                                  CCP-30CF.sub.3                                                                          5.0%                                                                  ECCP-3F.F                                                                               5.0%                                                                  BCH-3F.F 5.0%                                                                  CP-33F   7.0%                                                                  CP-35F   7.0%                                                                  CP-55F   6.0%                                                                  CPTP-301 4.0%                                                                  CPTP-302 4.0%                                                                  ______________________________________                                    

EXAMPLE 16

An STN mixture comprising

    ______________________________________                                         ME2N.F   6.0%      S→N:    <-40° C.                              ME3N.F   6.0%      Clearing point:                                                                               +95.5° C.                             ME4N.F   10.0%     Δn [589 nm; 20° C.]:                                                             +0.1213                                      ME5N.F   10.0%     HTP (S-811):   -11.6                                        ME7N.F   7.0%      Mux:           16                                           HP-3N.F  5.0%      Twist:         220°                                  HP-4N.F  5.0%      V.sub.(10,0,20) :                                                                             1.07 V                                       HP-5N.F  5.0%                                                                  CCH-301  13.0%                                                                 CC-5-V   18.0%                                                                 CP-33F   4.0%                                                                  CCPC-33  4.0%                                                                  CCPC-34  4.0%                                                                  CCPC-35  3.0%                                                                  ______________________________________                                    

EXAMPLE 17

An STN mixture comprising

    ______________________________________                                         ME2N.F   2.0%      S→N:    <-40° C.                              ME3N.F   3.0%      Clearing point:                                                                               111.0° C.                             PCH-3    20.0%     Δn [589 nm; 20° C.]:                                                             +0.1310                                      PCH-5    7.0%      HTP (S-811):   -10.3                                        CC-5-V   14.0%     Twist:         240°                                  CCP-20CF.sub.3                                                                          4.0%      V.sub.(10,0,20) :                                                                             2.29 V                                       CCP-30CF.sub.3                                                                          6.0%      d/p:           0.52                                         CP-33F   5.0%      d · Δn:                                                                        0.87                                         CP-35F   5.0%                                                                  ECCP-3F.F                                                                               6.0%                                                                  ECCP-5F.F                                                                               6.0%                                                                  PTP-102  3.0%                                                                  CPTP-301 4.0%                                                                  CPTP-302 3.0%                                                                  CPTP-303 3.0%                                                                  CBC-33F  5.0%                                                                  CBC-53F  4.0%                                                                  ______________________________________                                    

EXAMPLE 18

An STN mixture comprising

    ______________________________________                                         ME2N.F   2.0%      S→N:    <-40° C.                              ME3N.F   3.0%      Clearing point:                                                                               109.5° C.                             ME4N.F   8.0%      Δn [589 nm; 20° C.]:                                                             +0.1331                                      PCH-3    22.0%     HTP (S-811):   -10.5                                        CC-5-V   17.0%     Twist:         240°                                  CCP-20CF.sub.3                                                                          4.0%      V.sub.(10,0,20) :                                                                             2.03 V                                       CCP-30CF.sub.3                                                                          4.0%      d/p:           0.52                                         CP-33F   5.0%      d · Δn:                                                                        0.87                                         CP-35F   5.0%                                                                  ECCP-3F.F                                                                               7.0%                                                                  CPTP-301 4.0%                                                                  CPTP-302 4.0%                                                                  CPTP-303 4.0%                                                                  CBC-33F  5.0%                                                                  CBC-53F  6.0%                                                                  ______________________________________                                    

EXAMPLE 19

An STN mixture comprising

    ______________________________________                                         ME2N.F   2.0%      S→N:    <-40° C.                              ME3N.F   3.0%      Clearing point:                                                                               109° C.                               ME4N.F   9.0%      Δn [589 nm; 20° C.]:                                                             +0.1306                                      PCH-3    20.0%     HTP (S-811):   -10.4                                        CC-5-V   18.0%     Twist:         240°                                  CCP-20CF.sub.3                                                                          4.0%      V.sub.(10,0,20) :                                                                             1.94 V                                       CCP-30CF.sub.3                                                                          4.0%                                                                  CP-33F   6.0%                                                                  CP-35F   5.0%                                                                  ECCP-3F.F                                                                               7.0%                                                                  CPTP-301 4.0%                                                                  CPTP-302 4.0%                                                                  CPTP-303 3.0%                                                                  CBC-33F  5.0%                                                                  CBC-53F  6.0%                                                                  ______________________________________                                    

EXAMPLE 20

An STN mixture comprising

    ______________________________________                                         PCH-3    12.0%     S→N:    <-40° C.                              ME2N.F   4.0%      Clearing point:                                                                               91° C.                                ME3N.F   4.0%      Δn [589 nm; 20° C.]:                                                             +0.1405                                      ME4N.F   14.0%     HTP (S-811) [1/μm]:                                                                        -11.3                                        ME5N.F   9.0%      d · Δn [μm]:                                                                0.95                                         HP-3N.F  5.0%      Twist:         180°                                  HP-SN.F  5.0%      V.sub.(10,0,20) [V]:                                                                          1.18                                         CC-5-V   22.0%     (V.sub.90 /V.sub.10 -1) · 100[%]:                                                    8.47                                         PTP-201  3.0%                                                                  CPTP-30CF.sub.3                                                                         4.0%                                                                  CP-33F   6.0%                                                                  CBC-33   4.0%                                                                  CBC-55   4.0%                                                                  ______________________________________                                    

EXAMPLE 21

A TN mixture comprising

    ______________________________________                                         ME2N.3   2.20%     S→N:    <-40° C.                              ME3N.F   1.72%     Clearing point:                                                                               +108° C.                              ME4N.F   4.04%     Δn [589 nm; 20° C.]:                                                             +0.0993                                      PYP-5F   7.84%     Twist:         90°                                   CCH-301  9.80%     V.sub.(10,0,20) :                                                                             2.26 V                                       CCH-303  5.88%     V.sub.90 /V.sub.10 :                                                                          46.1%                                        CCH-501  3.92%     d · Δn [μm]:                                                                0.5                                          PCH-301  3.82%                                                                 BCH-3F.F 8.82%                                                                 CC-5-V   12.74%                                                                CP-33F   4.90%                                                                 CP-35F   4.90%                                                                 CP-55F   4.90%                                                                 CH-33    3.92%                                                                 CBC-33   3.92%                                                                 CBC-53   1.96%                                                                 CBC-55   2.94%                                                                 CBC-33F  2.94%                                                                 CCPC-33  1.96%                                                                 CCPC-34  3.92%                                                                 CCPC-35  1.96%                                                                 CCH-34   1.00%                                                                 ______________________________________                                    

EXAMPLE 22

Two-bottle system

    ______________________________________                                         Mixture I         Mixture II                                                   ______________________________________                                         ME2N.F      3.0%      K6            5.0%                                       ME3N.F      3.0%      ME2N.F        3.0%                                       ME4N.F      5.0%      ME3N.F        3.0%                                       MESN.F      4.0%      ME4N.F        7.0%                                       PCH-3       5.0%      PCH-301       17.0%                                      PCH-301     15.0      CC-5-V        16.0%                                      CC-5-V      18.0%     PTP-102       5.0%                                       PTP-102     4.0%      PTP-201       5.0%                                       CCP-30CF.sub.3                                                                             5.0%      BCH-3F.F      8.0%                                       ECCP-3F.F   5.0%      CP-33F        5.0%                                       BCH-3F.F    5.0%      CP-35F        5.0%                                       CP-33F      7.0%      CPTP-301      4.0%                                       CP-35F      7.0%      CPTP-302      5.0%                                       CP-5SF      6.0%      CPTP-303      4.0%                                       CPTP-301    4.0%      CPTP-30CF.sub.3                                                                              4.0%                                       CPTP-302    4.0%      CPTP-50CF.sub.3                                                                              4.0%                                       S→N: <-40° C.                                                                          S→N:   <-40° C.                            Clearing point:                                                                            87.5° C.                                                                          Clearing point:                                                                              86° C.                              Δn [589 nm; 20° C.]:                                                          +0.1215   Δn [589 nm; 20° C.]:                                                            +0.1599                                    HTP (S-811) [1/μm]:                                                                     -10.5     HTP (S-811) [1/μm]:                                                                       -10.5                                      Twist:      220°                                                                              Twist:        220°                                V.sub.(10,0,20) [V]:                                                                       2.01      V.sub.(10,0,20) [V]:                                                                         2.01                                       (V.sub.90 /V.sub.10-1) · 100[%]:                                                  6.0       (V.sub.90 /V.sub.10-1) · 100[%]:                                                    6.0                                        ______________________________________                                    

EXAMPLE 23

    ______________________________________                                         PCH-3N.F.F                                                                              12.0%     S→N:    <-40° C.                              PCH-5N.F.F                                                                              10.0%     Clearing point:                                                                               +69.5° C.                             PCH-3    20.0%     Δn [589 nm; 20° C.]:                                                             +0.1202                                      PCH-4    12.0%     Δε [kHz, 20° C.]:                                                        17.3                                         K9       3.0%      Twist:         90°                                   HP-3N.F  4.0%      V.sub.(10,0,20) :                                                                             1.16 V                                       HP-4N.F  3.0%                                                                  HP-5N.F  3.0%                                                                  CC-5-V   3.0%                                                                  CCG-V-F  15.0%                                                                 CBC-33F  3.0%                                                                  CBC-53F  3.0%                                                                  CBC-55F  3.0%                                                                  CBC-33   4.5%                                                                  ______________________________________                                    

EXAMPLE 24

    ______________________________________                                         PCH-3N.F.F                                                                              10.0%     S→N:    <-40° C.                              PCH-5N.F.F                                                                              10.0%     Clearing point:                                                                               +67.5° C.                             K6       7.0%      Δn [589 nm; 20° C.]:                                                             +0.1509                                      K9       7.0%      Δε [kHz, 20° C.]:                                                        17.7                                         K12      7.0%      Twist:         90°                                   PCH-3    20.0%     V.sub.(10,0,20) :                                                                             1.13 V                                       HP-3N.F  3.0%                                                                  HP-4N.F  3.0%                                                                  HP-5N.F  2.0%                                                                  ME15     3.0%                                                                  PTP-102  4.0%                                                                  CCG-V-F  7.0%                                                                  CBC-33F  3.0%                                                                  CBC-53F  3.0%                                                                  CBC-55F  3.0%                                                                  CBC-33   2.0%                                                                  CBC-53   3.0%                                                                  CBC-55   3.0                                                                   ______________________________________                                    

EXAMPLE 25

    ______________________________________                                         ME2N.F   8.0%      S→N:    <-40° C.                              ME3N.F   9.0%      Clearing point:                                                                               94.5                                         ME4N.F   10.0%     Δn [589 nm; 20° C.]:                                                             +0.1328                                      ME5N.F   10.0%     HTP S-811:     -12.1                                        PCH-3N.F.F                                                                              10.0%     Twist:         240°                                  CC-5-V   6.0%      V.sub.(10,0,20) :                                                                             1.13 V                                       CCG-V-F  15.0%                                                                 CCP-V-1  10.0%                                                                 CPTP-301 3.0%                                                                  CCPC-33  5.0%                                                                  CCPC-34  5.0%                                                                  CCPC-35  4.0%                                                                  CBC-33   5.0%                                                                  ______________________________________                                    

EXAMPLE 26

    ______________________________________                                         PCH-3N.F.F                                                                              12.0%     S→N:    <-40° C.                              PCH-5N.F.F                                                                              10.0%     Clearing point:                                                                               +69.5                                        PCH-3    20.0%     Δn [589 nm; 20° C.]:                                                             +0.1202                                      PCH-4    12.0%     Δε [kHz, 20° C.]:                                                        17.3                                         K9       3.0%      Twist:         90°                                   HP-3N.F  4.0%      V.sub.(10,0,20) :                                                                             1.16 V                                       HP-4N.F  3.0%                                                                  HP-5N.F  3.0%                                                                  CC-5-V   4.5%                                                                  CCG-V-F  15.0%                                                                 CBC-33F  3.0%                                                                  CBC-53F  3.0%                                                                  CBC-55F  3.0%                                                                  CBC-33   4.5%                                                                  ______________________________________                                    

EXAMPLE 27

Four-bottle system

    ______________________________________                                         Mixture I             Mixture II                                               ______________________________________                                         ME2N.F      9.0%      ME2N.F        9.0%                                       ME3N.F      9.0%      ME3N.F        9.0%                                       ME4N.F      10.0%     ME4N.F        10.0%                                      ME5N.F      8.0%      ME5N.F        8.0%                                       PCH-3N.F.F  10.0%     PCH-3N.F.F    10.0%                                      CC-5-V      6.0%      CCG-V-F       13.0%                                      CCG-V-F     16.0%     CCP-V-1       12.0%                                      CCP-V-1     11.0%     PTP-102       5.0%                                       CPTP-301    2.0%      CPTP-301      5.0%                                       CCPC-33     5.0%      CPTP-302      5.0%                                       CCPC-34     5.0%      CPTP-303      5.0%                                       CCPC-35     5.0%      CBC-33        3.0%                                       CBC-33      2.0%      CBC-53        2.0%                                       CBC-33F     2.0%      CBC-33F       2.0%                                       CBC-53F     2.0%      CBC-53F       2.0%                                       S→N: <-40° C.                                                                          S→N:   <-40° C.                            Clearing point:                                                                            +94.5° C.                                                                         Clearing point:                                                                              +94.0° C.                           Visc. +20° C.:                                                                      38        Visc. +20° C.:                                                                        43                                         Δn [589 nm; 20° C.]:                                                          0.1292    Δn [589 nm; 20° C.]:                                                            0.1700                                     HTP (S-811):                                                                               -12.3     HTP S-811:    -12.0                                      Twist:      240°                                                                              Twist:        240°                                V.sub.(10,0,20) [V]:                                                                       1.14      V.sub.(10,0,20) [V]:                                                                         1.11                                       (V.sub.90 /V.sub.10-1) · 100[%]:                                                  5.3       (V.sub.90 /V.sub.20-1) · 100[%]:                                                    6.3                                        ______________________________________                                         Mixture III           Mixture IV                                               ______________________________________                                         ME2N.F      2.0%      ME2N.F        2.0%                                       ME3N.F      3.0%      ME3N.F        3.0%                                       ME4N.F      4.0%      ME4N.F        4.0%                                       PCH-3N.F.F  10.0%     PCH-3N.F.F    10.0%                                      CC-5-V      18.0%     CC-5-V        9.0%                                       CCG-V-F     24.0%     CCG-V-F       19.0%                                      CCP-V-1     12.0%     CCP-V-1       13.0%                                      CCP-V2-1    6.0%      CCP-V2-1      4.0%                                       PTP-102     5.0%      PTP-102       5.0%                                       PTP-201     5.0%      PTP-201       5.0%                                       CPTP-301    4.0%      PTP-301       5.0%                                       CPTP-302    3.0%      PTP-302       5.0%                                       CCPC-33     4.0%      CPTP-301      5.0%                                                             CPTP-302      5.0%                                                             CPTP-303      5.0%                                       S→N: <-40° C.                                                                          S→N:   <-40° C.                            Clearing point:                                                                            +94.5° C.                                                                         Clearing point:                                                                              +95.0° C.                           Visc. +20° C.:                                                                      17        Visc. +20° C.:                                                                        20                                         Δn [589 nm; 20° C.]:                                                          0.1286    Δn [589 nm; 20° C.]:                                                            0.1697                                     HTP (S-811):                                                                               -10.8     HTP S-811:    -10.5                                      Twist:      240°                                                                              Twist:        240°                                V.sub.(10,0,20) [V]:                                                                       1.96      V.sub.(10,0,20) [V]:                                                                         1.95                                       (V.sub.90 /V.sub.10-1) · 100[%]:                                                  5.1       (V.sub.90 /V.sub.10-1) · 100[%]:                                                    6.2                                        ______________________________________                                    

EXAMPLE 28

Two-bottle system

    ______________________________________                                         Mixture I         Mixture II                                                   ______________________________________                                         ME2N.F      10.0%     ME2N.F       6.0%                                        ME3N.F      10.0%     ME3N.P       6.0%                                        ME4N.F      11.0%     ME4N.F       10.0%                                       ME5N.F      10.0%     ME5N.F       6.0%                                        CC-5-V      14.0%     CC-5-V       19.5%                                       CCG-V-F     22.0%     CCG-V-F      25.0%                                       CPTP-301    4.0%      PTP-102      4.0%                                        CCPC-33     5.0%      PTP-201      3.0%                                        CCPC-34     5.0%      CPTP-301     3.5%                                        CCPC-35     5.0%      CCPC-33      5.0%                                        CBC-33      2.0%      CCPC-34      5.0%                                        CBC-33F     2.0%      CCPC-35      4.0%                                                              CBC-33       3.0%                                        S→N: <-40° C.                                                                          S→N:  <-40° C.                             Clearing point:                                                                            +100.5° C.                                                                        Clearing point:                                                                             +103.0° C.                           Visc. +20° C.:                                                                      37        Visc. +20° C.:                                                                       25                                          Δn [589 nm; 20° C.]:                                                          0.1315    Δn [589 nm;                                                                           0.1310                                                            20° C.]:                                          HTP S-811:  -12.0     HTP S-811:   -11.1                                       Twist:      240°                                                                              Twist:       240°                                 V.sub.(10,0,20) [V]:                                                                       1.19      V.sub.(10,0,20) [V]:                                                                        1.52                                        (V.sub.90 /V.sub.10-1) · 100[%]:                                                  6.7       (V.sub.90 /V.sub.10-2) ·                                                           5.3                                                               100[%]:                                                  ______________________________________                                    

EXAMPLE 29

Two-bottle system

    ______________________________________                                         Mixture I         Mixture II                                                   ______________________________________                                         ME2N.F      9.0%      ME2N.F        3.0%                                       ME3N.F      5.0%      ME3N.F        3.0%                                       ME4N.F      11.0%     ME4N.F        5.0%                                       ME5N.V      11.0%     MESN.F        5.0%                                       CC-5-V      19.0%     CC-5-V        22.0%                                      PTP-102     2.0%      PCH-301       18.0%                                      CCG-V-F     18.0%     PTP-102       3.0%                                       CPTP-302    3.0%      CCG-V-F       12.0%                                      CCPC-33     5.0%      BCH-32        10.0%                                      CCPE-34     5.0%      CPTP-301      3.0%                                       CCPC-35     5.0%      CPTP-302      4.0%                                       CBC-33F     3.0%      CBC-33        5.0%                                                             CBC-53        5.0%                                                             CBC-33F       2.0%                                       S→N: <-40° C.                                                                          S→N:   <-40° C.                            Clearing point:                                                                            +94.5° C.                                                                         Clearing point:                                                                              +95.0° C.                           Visc. +20° C.:                                                                      31        Visc. +20° C.:                                                                        16                                         Δn [589 nm; 20° C.]:                                                          +0.1295   Δn [589 nm; 20° C.]:                                                            +0.1295                                    Twist:      90°                                                                               Twist:        90°                                 V.sub.(10,0,20) [V]:                                                                       1.06      V.sub.(10,0,20) [V]:                                                                         2.07                                       (V.sub.90 /V.sub.10-1) · 100[%]:                                                  45.3      (V.sub.90 /V.sub.10-1) · 100[%]:                                                    40.1                                       ______________________________________                                    

EXAMPLE 30

    ______________________________________                                         ME2N.F   2.0%      S→Ni    <-40                                         ME3N.F   2.0%      Clearing point:                                                                               +95.5° C.                             ME5N.F   3.0%      Δn [589 nm; 20° C.]:                                                             +0.1297                                      CC-5-V   20.0%     Twist:         90°                                   CCH-34   8.0%      V.sub.(10,0,20) [V]:                                                                          3.01                                         PCH-301  12.0%     V.sub.90 /V.sub.10-1) · 100[%]:                                                      39.9                                         PTP-102  4.0%                                                                  PTP-201  5.0%                                                                  CCG-V-F  12.0%                                                                 CP-33F   7.0%                                                                  CP-35F   7.0%                                                                  BCH-32   6.0%                                                                  CPTP-301 4.0%                                                                  CPTP-302 4.0%                                                                  CPTP-303 4.0%                                                                  ______________________________________                                    

EXAMPLE 31

    ______________________________________                                         PCH-3N.F.F                                                                              13.0%     S→N     <-40                                         ME2N.F   3.0%      Clearing point:                                                                               +68.0° C.                             ME3N.F   3.0%      Δn [589 nm; 20° C.]:                                                             +0.1503                                      K6       8.0%      Twist:         90°                                   K9       8.0%      V.sub.(10,0,20) [V]:                                                                          1.15                                         K12      7.0%      V.sub.90 /V.sub.10-1) · 100[%]:                                                      40.9                                         PCH-3    13.0%                                                                 HP-3N.F  4.0%                                                                  HP-4N.F  3.0%                                                                  HP-5N.F  2.0%                                                                  CC-5-V   7.0%                                                                  ME15     11.0%                                                                 CBC-33F  3.0%                                                                  CBC-53F  3.0%                                                                  CBC-55F  3.0%                                                                  CBC-33   3.0%                                                                  CBC-53   3.0%                                                                  CBC-55   3.0%                                                                  ______________________________________                                    

The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. 

What is claimed is:
 1. A liquid-crystal display containingtwo outer plates which, together with a frame, form a cell, a nematic liquid-crystal mixture of positive dielectric anisotropy which is present in the cell, electrode layers with alignment layers on insides of the outer plates, a pretilt angle between a longitudinal axis of molecules at a surface of the outer plates and the outer plates of from 8 degree to 30 degrees, and a twist angle of the liquid-crystal mixture in the cell from alignment layer to alignment layer with a value of between 22.5° and 600°, a chiral nematic liquid-crystal mixture comprisinga) 20-90% by weight of a liquid-crystalline component A consisting of one or more compounds having a dielectric anisotropy of greater than +1.5; b) 10-65% by weight of a liquid-crystalline component B consisting of one or more compounds having a dielectric anisotropy of -1.5 to +1.5; c) 0-20% by weight of a liquid-crystalline component D consisting of one or more compounds having a dielectric anisotropy of below -1.5, and d) 0-5% by weight of an optically active component C in such an amount that the ratio of the cell gap and the natural pitch of the chiral nematic liquid-crystal mixture is from about 0.2 to 1.3, wherein component A comprises at least one component of the formula IA ##STR82## in which R^(a) is an alkyl group having 1 to 12 carbon atoms, in which, in addition, one or two non-adjacent CH₂ groups may be replaced by --O--, --CH═CH--, --CO--, --OCO-- or --COO--, L is H or F, and r is 0 to 1, and component B comprises at least one compound of the formula IB ##STR83## in which R^(b) is an alkenyl radical having 2 to 12 carbon atoms, R^(c) is F, or an unsubstituted or at least monofluoro-substituted alkyl or alkoxy radical having 1-6 carbon atoms, ##STR84## are each, independently of one another, ##STR85## l is 0 or 1, and L¹ and L² are each, independently of one another, H or F.
 2. A display according to claim 1, wherein component B comprises at least one compound of subformulae IB1 to IB6: ##STR86## wherein R^(c') is a straight-chain alkyl or alkoxy radical having 1-6 carbon atoms, andR^(d) is H, CH₃, C₂ H₅ or n-C₃ H₇.
 3. A display according to claim 1, wherein component A additionally comprises compounds of formulae II and/or III ##STR87## in which R is an alkyl group having 1 to 12 carbon atoms, in which, in addition, one or two non-adjacent CH₂ groups may be replaced by --O--, --CH═CH--, --CO--, --OCO or --COO--, ##STR88## are each, independently of one another, ##STR89## L¹⁻⁶ are each, independently of one another, H or F, Z¹ is --COO--, --CH₂ CH₂ -- or a single bond,Z² is --CH₂ CH₂ --, --CH₂ O--, --COO--, --C.tbd.C-- or a single bond, Q is --CF₂ --, --CHF--, OCF₂, --OCF-- or a single bond, Y is F or Cl a is 1 or 2, and b is 0 to
 1. 4. A display according to claim 3, wherein component A comprises at least one compound of formula IIa to IId ##STR90## where R, L¹, L², L⁵, are as defined above.
 5. A display according to claim 1, wherein component B further comprises at least one of formulae IV1 to IV24: ##STR91## in which R¹ and R² are each, independently of one another, an alkyl group having 1 to 12 carbon atoms, in which, in addition, one or two non-adjacent CH₂ groups may be replaced by --O--, --CH═CH--, --CO--, --OCO or --COO--.
 6. A display according to claim 1, wherein the liquid-crystal mixture further comprises one or more compounds of formula B1IIIa ##STR92## in which R^(3') is CH₃ --(CH₂)_(o), CH₃ --(CH₂)_(o) --O--, CH₃ --(CH₂)_(p) --, trans-H-(CH₂)_(q) --CH═CH--(CH₂ CH₂)_(b) --CH₂ O--, trans-H-(CH₂)_(q) --CH═CH--(CH₂ CH₂)_(b) --, or CH₃ --(CH₂)_(o) --O--CH₂ --,R^(4') is CH₃ --(CH₂)_(p) -- o is 0, 1, 2 3 or 4, q is 0, 1, 2 or 3, b is 0 to 1, and p is 1, 2, 3 or
 4. 7. A display according to claim 1, wherein component B further comprises at least one compound of formulae Xa to XIIIa: ##STR93## in which Alkyl and Alkoxy are a straight-chain alkyl or alkoxy radical having 1 to 7 carbon atoms.
 8. A display according to claim 1, wherein component A further comprises at least one compound of formula T3 ##STR94## in which R⁷ is --C_(x) H_(2x+1), --OC_(x) H_(2x+1), ##STR95## x is an integer from 1-15, L¹, L², L⁵, and L⁶ are each, independently of one another, H or F, andX' is F, Cl or OCF₃.
 9. A liquid-crystal mixture comprisinga) 20-90% by weight of a liquid-crystalline component A consisting of one or more compounds having a dielectric anisotropy of greater than +1.5; b) 10-65% by weight of a liquid-crystalline component B consisting of one or more compounds having a dielectric anisotropy of -1.5 to +1.5; c) 0-20% by weight of a liquid-crystalline component D consisting of one or more compounds having a dielectric anisotropy of below -1.5, and d) 0-5% by weight of an optically active component C in such an amount that the ratio of the cell gap and the natural pitch of the chiral nematic liquid-crystal mixture is from about 0.2 to 1.3, when placed in a cell havingelectrode layers with alignment layers on insides of the outer plates, a pretilt angle between a longitudinal axis of molecules at a surface of the outer plates and the outer plates of from 8 degree to 30 degrees, and a twist angle of the liquid-crystal mixture in the cell from alignment layer to alignment layer with a value of between 22.5° and 600°, wherein component A comprises at least one component of the formula IA ##STR96## in which R^(a) is an alkyl group having 1 to 12 carbon atoms, in which, in addition, one or two non-adjacent CH₂ groups may be replaced by --O--, --CH═CH--, --CO--, --OCO-- or --COO--, L is H or F, and r is 0 to 1, and component B comprises at least one compound of the formula IB ##STR97## in which R^(b) is an alkenyl radical having 2 to 12 carbon atoms, R^(c) is F, or an unsubstituted or at least monofluoro-substituted alkyl or alkoxy radical having 1-6 carbon atoms, ##STR98## are each, independently of one another, ##STR99## l is 0 or 1, and L¹ and L² are each, independently of one another, H or F.
 10. A mixture according to claim 9, wherein component B comprises at least one compound of subformulae IB1 to IB6: ##STR100## wherein R^(c') is a straight-chain alkyl or alkoxy radical having 1-6 carbon atoms, andR^(d) is H, CH₃, C₂ H₅ or n-C₃ H₇.
 11. A mixture according to claim 9, wherein component A additionally comprises compounds of formulae II and/or III ##STR101## in which R is an alkyl group having 1 to 12 carbon atoms, in which, in addition, one or two non-adjacent CH₂ groups may be replaced by --O--, --CH═CH--, --CO--, --OCO-- or --COO--, ##STR102## are each, independently of one another, ##STR103## L¹⁻⁶ are each, independently of one another, H or F, Z¹ is --COO--, --CH₂ CH₂ -- or a single bond,Z² is --CH₂ CH₂ --, --CH₂ O--, --COO--, --C.tbd.C-- or a single bond, Q is --CH₂ --, --CHF--, OCF₂, --OCHF-- or a single bond, Y is F or Cl a is 1 or 2, and b is 0 to
 1. 12. A mixture according to claim 11, wherein component A comprises at least one compound of formula IIa to IId ##STR104## where R, L¹, L², L⁵, are as defined above.
 13. A mixture according to claim 9, wherein component B further comprises at least one of formulae IV1 to IV24: ##STR105## in which R¹ and R² are each, independently of one another, an alkyl group having 1 to 12 carbon atoms, in which, in addition, one or two non-adjacent CH₂ groups may be replaced by --O--, --CH═CH--, --CO--, --OCO or --COO--.
 14. A mixture according to claim 9, wherein the liquid-crystal mixture further comprises one or more compounds of formula B1IIIa: ##STR106## in which R^(3') is CH₃ --(CH₂)_(o), CH₃ --(CH₂)_(o) --O--, CH₃ --(CH₂)_(p) --, trans-H-(CH₂)_(q) --CH═CH--(CH₂ CH₂)_(b) --CH₂ O--, trans-H-(CH₂)_(q) --CH═CH--(CH₂ CH₂)_(b) --, or CH₃ --(CH₂)_(o) --O--CH₂ --,R^(4') is CH₃ --(CH₂)_(p) -- o is 0, 1, 2 3 or 4, q is 0, 1, 2 or 3, b is 0 to 1, and p is 1, 2, 3 or
 4. 15. A mixture according to claim 9, wherein component B further comprises at least one compound of formulae Xa to XIIIa: ##STR107## in which Alkyl and Alkoxy are a straight-chain alkyl or alkoxy radical having 1 to 7 carbon atoms.
 16. A mixture according to claim 9, wherein component A further comprises at least one compound of formula T3 ##STR108## in which R⁷ is --C_(x) H_(2x+1), --OC_(x) H_(2x+1), ##STR109## x is an integer from 1-15, L¹, L², L⁵, and L⁶ are each, independently of one another, H or F, andX' is F, Cl or OCF₃. 